Iowa State University researchers tested different fitness bands that make it easy for anyone with weight loss or other health goals to track their physical activity and calories burned.

According to a news release from the university, the bands come in a variety of shapes, colors and sizes, but an ISU study found not all devices are created equal.

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Researchers tested eight different activity monitors to determine the accuracy of each model.

Kinesiology professor Gregory Welk said a majority of the devices provided reasonably accurate estimates, within 10 to 15 percent, of calories burned.

Welk said activity monitors were once a tool used only by researchers. Now the market has exploded in response to consumer demand. The monitors can be a motivational tool for some, while others like the convenience for tracking.

Researchers know that people tend to overestimate their activity levels, so it is important that the monitors are accurate to eliminate that human error.

“People buy these activity monitors assuming they work, but some of them are not that accurate or have never been tested before. These companies just produce a nice-looking device with a fancy display and people buy it,” Welk said.

According to the research, the BodyMedia FIT was the top performer with a 9.3 percent error rating, which is comparable to research models, Welk said. The Fitbit Zip and Fitbit One were next with a 10.1 and 10.4 percent error rating, respectively. Other models included the Jawbone Up (12.2 percent), Actigraph (12.6 percent), Directlife (12.8 percent), Nike Fuel Band (13.0 percent) and Basis Band (23.5 percent).

To test the devices, 30 men and 30 women wore all eight monitors during a 69-minute workout that included a series of 13 different activities, ranging from writing at a computer and playing Wii tennis to playing basketball and running.

Participants also wore a portable metabolic analyzer that researchers used for comparison to test the accuracy of each device.

The research, published in the journal Medicine & Science in Sports & Exercise, assessed how the devices performed for a sustained period of monitoring, instead of evaluating individual activities, to better reflect how they would perform in real-world conditions.

Welk also points out that the monitors, regardless of accuracy, cannot guarantee results in reaching fitness goals, and what works for one person may not work for another.